Elastic fluid condenser



Oct. 19, 1943. R. H. NORRIS ELASTIC FLUID CONDENSER Filed Jan. 16, 1941 I nventor Rollin H. Norris, y 6W l-fis Attorney.

Patented Oct. 19, 1943 ELASTIC FLUID CONDENSER Rollin H. Norris, Schenectady, N. Y., asslgnor to General Electric Company, a corporation of New York Application January 16, 1941, Serial No. 374,727

9 Claims.

The present invention relates to elastic fluid condensers, more particularly to surface type heat exchangers having rows of tubes for receiving steam or other elastic fluid to be condensed. The invention is of particular significance in connection with finned tube condenserssuch as are used in locomotives in which the condensation is effected by a stream of cooling air forced across the tubes. In the design of such condensers the air pressure drop required for a given performance and a given surface area can be reduced by the reduction of the width or diameter of the condenser tubes. Heretofore the trend of reducing the width or diameter of the condenser tubes has been limited in view of the formation of slugs of condensate within tubes of small cross-section. Ordinarily the condensate flows as a film along the inside surfaces of the tubes. This film depending upon the surface tension of the liquid may not drop off the lower end of the tube but collect as a drop or slug. If the tube is sufficiently small, this drop may completely cover the cross-section of the tube. As more condensation is formed and added to the top of this slug, a drop of condensate, such as water in the case of a steam condenser, will fall off the lower surface of this slug without breaking the slug itself. Therefore any air which enters the tube with the elastic fluid will accumulate above the slug in the lower end of the tube and reduce the heat transfer through the tube. During low load condition, especially in case the condenser forms part of a locomotive operated during winter, the small percentage of non-condensable gas carried with the steam may accumulate above the slug and allow the slug to freeze and thereby put the tube out of operation. Accordingly, it becomes important to prevent the formation of slugs at the lower ends of condenser tubes and the freezing of condensate within the tubes.

The object of my invention is to provide an improved construction and arrangement of elastic fluid condensers whereby the formation of slugs at the lower ends of condenser tubes or passages and the freezing of condensate at the lower ends of such tubes or passages are substantially eliminated.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing. I

In the drawing Fig. 1 illustrates an elastic fluid condenser embodying my invention; Fig. 2 is an Ill enlarged cross-sectional view of a tube arrangement forming part of Fig. 1; Fig 3 is-a section through the horizontal centerline of Fig. 2; and Figs. 4 and 5 show modifications according to my invention.

The elastic fluid condenser as shown in Fig. 1 comprises a. plurality of tube arrangements ill.

Each tube arrangement includes an outer or main tube H and an inner or auxiliary tube l2. The tubes are connected to an uppor header l3 which forms two chambers, a lower chamber l4 and an upper chamber IS. The chambers I4 and have inlet conduits l6 and I! respectively for receiving elastic fluid to be condensed. The outer tubes H are connected to the bottom of the header l3 to receive elastic fluid from the chamber 54, whereas the inner tubes l2 are connected to receive elastic fluid from the chamber IS. The lower ends of the outer tubes II are connected to openings in a lower header I8, which latter has a discharge conduit for condensate l9. In the present example the outer tubes are streamlined or oval-shaped in cross-section to reduce the pressure drop across the condenser. The

outer tubes ll project into the lower header 58.

More specifically, one side of the outer tubes ll projects more than the other side or, from another viewpoint, the outer tubes have lower end portions with projections formed on one side thereof. This projection in the example of Figs. 1 to 3 is formed by slanting the end face of the outer tube. In other words, the outer tubes according to my invention have end faces which deviate from the horizontal plane. The deviation is indicated in Fig. 3 by a reference character 20. This deviation in order to be efiective must be sufiicient to prevent the formation of slugs of liquid with the surface tension of the particular fluid with which the condenser is operated. Thus, the projection to be formed on one side of a tube may be suflicient to prevent the formation of slugs of water covering the end face of the tube but not sufficient to prevent the formation of slugs of another liquid.

As pointed out above, in certain cases it is important to prevent the formation of ice along the inner surface of steam condenser tubes. This formation takes place primarily near the lower end of the tubes during low load condition and low outside temperatures. This is ac complished in accordance with my invention by the provision of the inner tubes l2 which are arranged so that the steam flowing therein passes down to the end of the tube with condensation of no more than a small fraction of the steam supplied to the inner tubes. If the major part of this steam were allowed to condense, as is likely to be th case in the outer tube, the partial pressure of non-condensable gases would rise, and thereby allow the partialpressure, and hence the saturation temperature, of the steam to drop. If the saturation temperature were to drop below 32 F., freezing would begin. To minimize condensation in the inner tube, the heat transfer between the inner and outer tubes is reduced by the provision of coatings or layers 2i of nonmetallic material with low heat-conductivity between the contacting surfaces of the inner and outer tubes. In the present example the inner tubes are connected to the separate chamber 15 and the pressure or temperature of the fluid therein may be higher than the pressure or the temperature respectively of the elastic fluid in the chamber I4. If freezing should begin in the outer tube, the ice would be prevented from fllling and bursting this outer tube since the ice would begin to melt when it became sufllciently thick to approach the steamheated inner tube. Thus, the inner tube broadly constitutes a means to heat the contents of the outer tube, or, from another viewpoint, to prevent the temperature of the contents of the outer tube from dropping below a predetermined value, that is, to keep the condensate in the outer tube from freezing solidly across the tube cross-section. Another important function of the inner tube is the support it gives the outer tube, especially where the outside of the outer tube is subject to atmospheric pressure and the interior of the outer tube is operated under vacuum. In such cases the outer tube may be made lighter by the provision of the inner tubes.

The arrangement of Fig. 4 comprises a plurality of tube arrangements, each arrangement including an outer, finned tube 25 and an inner tube 26. The upper or inlet ends of the outer tubes are connected to a chamber 21 having an inlet 28 for elastic fluid and the upper or inlet ends of the inner tubes 26 are connected to a chamber 29 having an inlet conduit 30 for receiving heating fluid. The lower ends of the outer tubes are connected to a lower header or chamber 3i having a discharge conduit for condensate 32 and the lower or outlet ends of the inner tubes 26 are connected to a chamber 33 having a discharge conduit 34. The two chambers or headers 3i and 33 form a unitary structure and the end portions of the inner tubes 26 project through the header or chamber 3! into the chamber 33. Thus, these end portions of the inner tubes 26 broadly constitute projections with regard to the outer tubes. As such projections they prevent the formation of slugs in the lower end portions of the outer tubes and in addition the inner tubes constitute heating tubes with regard to the outer tubes to prevent freezing in the lower end portions of the outer tubes. As the outer tubes in th arrangement of Fig. 4 are connected to separate upper and lower chambers 29, 33 they may be operated with a heating medium other than the elastic fluid to be condensed in the outer tubes 25.

Fig. shows a tube arrangement including an outer, flat tube 40 having substantially parallel front and rear walls 4|. The lower end of the tub 40 has one side or portion projecting beyond the other side or portion. Such projections in the present example are formed by two lugs 42 on the front and rear walls 4i. These lugs prevent the formation of l gs-at the lower end of the tube 40. Slug formation is further prevented in this arrangement by the provision of an inner tube 43 which in the present example is rectangular or square in cross-section and has a lower end portion projecting beyond the lower end of the tube 40. The inner side walls of the outer tube 40 engage the outer side walls of the inner tube 43.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Air cooled elastic fluid condenser for locomotives and like power plants in which the cooling air temperature varies considerably comprising a plurality of tube arrangements each including an outer and an inner tube, separate headers for conducting elastic fluid to the inlets of the outer and inner tubes, one tube of each arrangement having an outlet end projecting beyond and communicating with the outlet end of the other tube, and a single header connected to the outlet ends of the inner and outer tubes.

2. Air cooled elastic fluid condenser for locomotives and like power plants in which the cooling air temperature varies considerably comprising inlet header means, a plurality of vertically extending tub arrangements each including an outer and an inner tube having inlets connected to the inlet header means, the inner tube engaging diametrically opposite portions of the outer tube, the outer tube extending beyond and communicating with the inner tube and having an end portion forming a projection on one side to prevent the formation of slugs of condensate, and a single outlet header connected to the outlet ends of the inner and outer tubes.

3. Air cooled elastic fluid condenser for locomotives and like power plants in which the cooling air temperature varies considerably comprising a plurality of substantially vertically extending tube arrangements each including an outer and an inner tube, an inlet header connected to the upper ends of the tubes, and an outlet header connected to the lower ends of the outer tubes, the inner tubes engaging diametrically opposite portions of the outer tubes, the lower ends of the outer tubes extending beyond the inner tubes and having an outlet face sufficiently inclined to prevent the formation of slugs of condensate in the outlet, the inner tubes having outlets discharging into the end portions of the outer tube.

4. Air cooled elastic fluid condenser for locomotives and like power plants in which the cooling air temperature varies considerably comprising a plurality of vertically extending tube arrangements each including an outer and an inner tube, inlet header means forming a chamber connected to the upper ends of the outer tubes and another chamber connected to the upper ends of the inner tubes, and outlet header means forming a chamber connected to the lower ends of the inner and outer tubes, the outer tubes being ovalshaped in cross-section and engaging diametrically opposite portions of the inner tubes to prevent freezing of fluid in the outer tubes.

5. Air cooled elastic fluid condenser for loco motives and like power plants in which the cool ing air temperatur varies considerably compris ing a pluarity of vertically extending tubes, header for receiving elastic fluid to. be con densed connected to the upper ends of the tubes and another header for receiving condensate connected to the lower ends of the tubes, one side of the outlet of each tube forming a projection with regard to the outer side of such outlet, said projection being located within the other ing air temperature varies considerably comprising a plurality of tubes, an upper header for receiving elastic fluid to be condensed connected to the inlets of the tubes, and an outlet header with a horizontally disposed flat top for receiving condensate connected to the outlets of the tubes, the outlet portion of each tube being sealed into an opening in said top and having a slanted end face sufliciently inclined towards the centerline of the tube to prevent the formation of slugs of condensate at the outlet.

7. A condenser tube arrangement for aircooled condensers comprisingan outer tube for receiving elastic fluid 'to be condensed, an inner tube surrounded by and having portions engaging the outer tube and communicating with the outlet of the latter for conducting heating fluid towards and discharging it into the outlet portion of the outer tube to prevent freezing of condensate in the outer tube, and heat-insulating material interposed between the engaging portions of the inner and outer tubes to reduc the heat transfer between them.

8. A condenser tube arrangement for aircooled condensers comprising an outer fiat tube having lug-forming end portions, and an inner tube engaging opposite flat surfaces of the outer tube, the outlet end of one tube extending beyond and communicating with the outlet nd of the other tube.

9. Surface type heat exchanger comprising a plurality of outer tubes substantially oval-shaped in cross-section, header means connected to the ends of the tubes, and means to reduce freezing near the outlet portions of said tubes and to support said tubes against collapse comprising an inner round tube for each of said-outer tubes, said inner tubes extending substantially the entire length of the outer tubes and having an outer diameter about qual to the small diameter of the outer tube.

ROLLIN H. NORRIS. 

